<template>
  <div class="goods-image">
    <!--大图:发大的,作为背景-->
    <div v-show="show" class="large" :style="[{backgroundImage:`url(${images[currIndex]})`},largePosition]"></div>
    <!--中图-->
    <div class="middle" ref="target">
      <img :src="images[currIndex]" alt="">
      <!--鼠标移上去的覆盖罩-->
      <div v-show="show" class="layer" :style="layerPosition"></div>
    </div>
    <!--小图-->
    <ul class="small">
      <li v-for="(img,i) in images" :key="img" :class="{active:i===currIndex}">
        <img @mouseenter="currIndex=i" :src="img" alt="">
      </li>
    </ul>
  </div>
</template>

<script>
import { reactive, ref, watch } from 'vue'
import { useMouseInElement } from '@vueuse/core'

export default {
  name: 'GoodsImage',
  props: {
    images: {
      type: Array,
      default: () => []
    }
  },
  setup () {
    //  当前预览图的索引
    const currIndex = ref(0)

    const {
      show,
      layerPosition,
      largePosition,
      target
    } = usePreviewImg()
    return {
      currIndex,
      show,
      layerPosition,
      largePosition,
      target
    }
  }
}
const usePreviewImg = () => {
  // 1. 是否显示覆盖罩和大图
  const show = ref(false)
  // 2.覆盖罩坐标(样式)
  const layerPosition = reactive({
    left: 0,
    top: 0
  })
  // 3.大图的背景定位
  const largePosition = reactive({
    backgroundPositionX: 0,
    backgroundPositionY: 0
  })
  // 4.使用useMouseInElement得到基于元素左上角的坐标和是否离开元素的数据
  const target = ref(null)
  // elementX 鼠标基于容器左上角X轴偏移
  // elementY 鼠标基于容器左上角Y轴偏移
  // isOutside 鼠标是否在模板容器外
  const {
    elementX,
    elementY,
    isOutside
  } = useMouseInElement(target)
  watch([elementX, elementY, isOutside], () => {
    // 5.根据得到的数设置样式的数据,和是否显示的数据
    show.value = !isOutside.value
    // 计算坐标
    const position = {
      x: 0,
      y: 0
    }
    if (elementX.value < 100) {
      position.x = 0
    } else if (elementX.value > 300) {
      position.x = 200
    } else {
      position.x = elementX.value - 100
    }
    if (elementY.value < 100) {
      position.y = 0
    } else if (elementY.value > 300) {
      position.y = 200
    } else {
      position.y = elementY.value - 100
    }
    // 给样式赋值
    layerPosition.left = position.x + 'px'
    layerPosition.top = position.y + 'px'
    largePosition.backgroundPositionX = -2 * position.x + 'px'
    largePosition.backgroundPositionY = -2 * position.y + 'px'
  })
  return {
    show,
    layerPosition,
    largePosition,
    target
  }
}
</script>

<style scoped lang="less">
.goods-image {
  width: 480px;
  height: 400px;
  position: relative;
  display: flex;
  z-index: 500;

  .large {
    position: absolute;
    top: 0;
    left: 412px;
    // 原来图片宽度
    width: 400px;
    height: 400px;
    box-shadow: 0 0 10px rgba(0, 0, 0, 0.1);
    background-repeat: no-repeat;
    // 背景宽度
    background-size: 800px 800px;
    background-color: #f8f8f8;
  }

  .middle {
    width: 400px;
    height: 400px;
    background: #f5f5f5;
    position: relative;
    cursor: move;

    .layer {
      width: 200px;
      height: 200px;
      background: rgba(0, 0, 0, .2);
      left: 0;
      top: 0;
      position: absolute;
    }
  }

  .small {
    width: 80px;

    li {
      width: 68px;
      height: 68px;
      margin-left: 12px;
      margin-bottom: 15px;
      cursor: pointer;

      &:hover, &.active {
        border: 2px solid @xtxColor;
      }
    }
  }
}
</style>
